Poor melt strength of high density polyethylene is a major factor which makes it difficult to produce foamed articles therefrom. In the past, polyethylene foams have been routinely made from high pressure-low density polyethylene (LDPE) which exhibits superior melt strength compared to that of the HDPE, at the same viscosities. The melt strength of HDPE can be increased simply by increasing the HDPE molecular weight. However, the increase in molecular weight is accompanied by an increase in melt viscosity, which interferes with processability and contributes to cell collapse in the foaming process. The highly branched nature and low viscosity at high shear of the LDPE provides for a desirable environment for foaming, as compared to the normally linear HDPE molecule.
Therefore, it is an object of the present invention to provide an HDPE suitable for foaming.